다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Doping problems in GaN and in AlGaN alloys are addressed on the basis of state-of-the-art first-principles calculations. For n-type doping we find that nitrogen vacancies are too high in energy to be incorporated during growth, but silicon and oxygen readily form donors. The properties of oxygen, including DX-center formation, support it as the main cause of unintentional n-type conductivity. For p-type doping we find that the solubility of Mg is the main factor limiting the hole concentration in GaN. We discuss the beneficial effects of hydrogen during acceptor doping. Compensation of acceptors by nitrogen vacancies may occur, becoming increasingly severe as x increases in Al_x Ga_(1-x)N alloys.

https://arxiv.org/pdf/cond-mat/9810385.pdf

Theory of Doping and Defects in III-V Nitrides

Quantum dot solar cells, as a promising candidate for the next generation solar cell technology, have received tremendous attention in the last 10 years. Some recent developments in epitaxy growth and device structures have opened up new avenues for practical quantum dot solar cells. Unfortunately, the performance of quantum dot solar cells is often plagued by marginal photon absorption. In this review, we focus on the recent progress made in enhancing optical absorption in quantum dot solar cells, including optimization of quantum dot growth, improving the solar cells structure, and engineering light trapping techniques.

/pdf/recent-progress-towards-quantum-dot-solar-cells-with-1hey47lgtw.pdf

Recent Progress Towards Quantum Dot Solar Cells with Enhanced Optical Absorption

Quinhydrone/methanol treatment for the measurement of carrier lifetime in crystalline silicon substrates has been investigated. To estimate the surface passivation effect, the lifetimes of the silicon substrates were measured using the microwave photoconductive decay method. The measured lifetime is dependent on quinhydrone concentration and passivation time. The 0.01 mol/dm3 quinhydrone/methanol treatment exhibited a good passivation effect, and a very low surface recombination velocity was obtained. The quinhydrone/methanol treatment can provide a reliable lifetime map of silicon wafers since a constant lifetime value without degradation can be obtained. Therefore, the quinhydrone/methanol treatment can be used for estimating the bulk lifetime of silicon substrates.

Quinhydrone/Methanol Treatment for the Measurement of Carrier Lifetime in Silicon Substrates : Semiconductors

Passive radiative sub-ambient cooling is an emerging field of futuristic research and development and has the potential to reduce water and electricity demands, and the negative environmental effects of conventional cooling systems. Nighttime radiative passive cooling was achieved even long before, and daytime passive radiative cooling has gained recent momentum in cooling technology due to the development of metamaterials. In this paper, materials of passive radiative cooling are described with fundamental physics applied to the interaction between the material and electromagnetic wave and material design. Structure of material is an important parameter to achieve daytime radiative cooling and hence three major material structure categories (multilayer structure, porous polymer, and randomly distributed structure) are discussed. Subsequently, the various fabrication processes and characterization of metamaterials for daytime radiative cooling are also described. Effects of various environmental factors like ambient temperature, cloud cover, moisture, pollution, wind velocity on radiative cooling performances are also discussed. The potential applications such as water cooling, space cooling, power plant condenser cooling, solar panel cooling and spacecraft cooling are described. Finally, various challenges of daytime radiative cooling are discussed and subsequently, future recommendations are provided, which may be useful for further research and development in this field.

Review on passive daytime radiative cooling: Fundamentals, recent researches, challenges and opportunities

High-temperature photovoltaics (PV) for terrestrial and extraterrestrial applications have presented demanding challenges for current solar cell materials, such as Si, III–V AlGaInP, and II–VI. Wid...

High-Temperature Polarization-Free III-Nitride Solar Cells with Self-Cooling Effects

Silicon Minority-carrier Lifetime Degradation During Molecular Beam Heteroepitaxial III-V Material Growth

Highly doped GaN p–n tunnel junction (TJ) contacts to InGaN solar cells are demonstrated, in which the TJs were grown by molecular beam epitaxy on top of active solar cell regions grown by metalorganic chemical vapor deposition. The effects of Si and Mg doping concentrations on solar cell characteristics are studied and used to improve turn-on voltage and series resistance. The highest doped cell with a TJ has an open-circuit voltage of 2.2 V, similar to that of the control cell fabricated using indium tin oxide (ITO), and a far less short-circuit current density loss from unwanted photogeneration in the TJ contact than in the ITO contact.

https://iopscience.iop.org/article/10.7567/APEX.11.082304/pdf

Chaomin Zhang

Papers

High-Temperature Polarization-Free III-Nitride Solar Cells with Self-Cooling Effects

Silicon Minority-carrier Lifetime Degradation During Molecular Beam Heteroepitaxial III-V Material Growth

InGaN solar cells with regrown GaN homojunction tunnel contacts

Improvement of GaP crystal quality and silicon bulk lifetime in GaP/Si heteroepitaxy

Temperature dependence of GaSb and AlGaSb solar cells